Drill bushing



Aug. s, 1944. F. FINKI 2,355,286

DRILL BUSHING` Filed April 24, 1942 Patented Aug. 8, 1944 UNITED-,I STATES PATENT OFFICE DRILL BUsHING Charles F. Fink, Baltimore, Md., assigner to Trimble & Fink Mfg'. Co., Inc., Baltimore, Md., a corporation of Maryland Application April 24, 1942, Serial N0. 440,390

3 Claims.

This invention relates to tool holders and more particularly to a bushing for holding a twist drill in place in the turret head of a screw machine.

The usual drill bushing for screw machines has been of a size to accommodate only a single drill. It has consequently been necessary to have on hand a large number of such drill bushings in order to accommodate the large number of different size drills which are available. Moreover, such drill bushings have not effectively held the drill for the reason that the drill was not clamped throughout the length of the bush- 1ng. i v Y With the bushing of the present invention a 'large number of varying sized drills may beheld sothat only a few different sized bushings will hold all of the 4drills which are available. Moreover, the entire length Aof the drill which is Within the bushing is rmly clamped by the bushing.

In the accompanying drawing:

Fig. 1 is a longitudinal sectional view, parts being shown in elevation, through a tool holder employed in the turret headof a screw machine, a drill bushing contemplated by the invention, being therein.

Fig. 2 is a View on the line 2--2 of Fig. 1.

Fig. 3 is a longitudinal'section through the drill bushingorFig. 1. f

Fig. 4 is a section on the line 4-4 of Fig. 3.

Fig. 5 is a plan view of the bushing of Figs. 3

and 4.

Fig. 6 is an end view ofa drill bushing for accommodating drills of a size smaller than those which are to be accommodated by the bushing of Figs. 3,'4 and Fig. 7 is a perspective view of the' bushing of Fig. 6, the parts being separated.

The carrier for the usual bushing holderof a screw machine is made of a face plate Ill and an integral attaching shank II. The shank Il of this carrier is of a size to fit into and be clamped securely in a socket in the turret head of a screw machine. The end face of the face plate I is perpendicular to the axis of the shank II. Threaded studs I2 project from this end face on diametrically opposite sides of the shank II.

The bushing holder is made up of a base flange I3 and an integral boss I4 having `a, socket I therein. Holes I6 are formed through the base plate I3` in line with the studs l2. These holes I6 should ybe considerably larger in diameter than the diameter of the studs I2 so that a limited movement of the bushing holder upon the face of the carrier Will be permitted. To clamp the flange I3 oi the bushing holder rmly against the face plate I0 in any set position, nuts Il may be tightened upon the studs I2. Y

Due to the at contact between the opposing facesrof the face plate I 0 and the base flange I3, the bushing holder may be moved about upon the face plate I Il within the limits afforded by the size of the holes I6, while maintaining at all times the parallelism of the axis of the boss I4. Thus, by loosening the nuts I1, the bushing holder may be moved to `a new position, Without disturbing the parallelism between the axis of the boss I4, and the axis of the shank II Through the side of the boss I4 passes a set screw 9. This set Vscrew is threaded into the boss I4 so that it may be used vto clamp a drill or tool` bushing in place in the socket I5. y

The drill bushing I8 of the invention is of an external size to snugly t within the socket I5 and the bushing I8 should have approximately the same length as the totallength of the bushing holder. As a feature of the invention, a slot is formed in the bushing I8 lengthwise thereof, so that the slot opens out notl only at the periphery of the bushing, butl opens at. the opposite ends of the vbushing I8 as well. The opposite side walls I9 of this slot are parallel to each otherand to a diametrical plane passing through the laxis of the bushing I8. The Width of the slotisnot critical, it being only necessary that the slot be wide enough to -accommodate the largest size drill which may be located in the bushing.`

`The bottomof the slot in bushing I8 should be of V-shape so that the faces 20 converge substantially to a meeting line which lies in the same diametrical plane with respect to which 'the sides I9, I9 are paralleled. This meeting line `further from the axis of the bushing I8.

To clamp in place a drill 2| which maybe located vat the bottom ofthe slot in bushing I8, a presser block 22 is provided. This presser block posite parallel sides of the block22. Joining theA face 23 with the opposite parallel sides of the presser block are inclined faces 24 which mayI convergence of the faces 20 determines the position of the drill at the bottom of the slot and the pressing action of the block 22 forces the drill into this position.

In Figs. 6 and 7 is shown the construction of a bushing 39 and presser block 3| which will accommodate drills of very small size. The slot in bushing 3D does not extend as deeply into the bushing 30`asdoes the slot in the bushing I8,

but otherwise its formation Yis the same. As is K apparent from Fig. 6, the meeting line of the have substantially the same inclination with rel' y spect to each other as do the faces at the i bottom of the slot.

The formation of the faces 24, 24`permits the f presser block 22 to descend deeper yinto the slot in the bushing I8 so that a smaller size drill than that shown in Fig. 4 'may be clamped in f place. It will be apparent that the width of the face 23 of the presser block is not critical inasmuch as this yface will have only a line contact with the drill. The thickness of the presser block 22 outwardly from the face 23 is determined by the'range of drill sizes which are intended to be accommodated by that particular presser block 22 and bushing I8. v

The presser block 22l may be prevented from displacement out of the slot by the provision of pins 25 Which are carried by the bushing I8.

These pins 25 project into the rslot from the op-.

posite walls I9 thereof, and preferably are at the opposite ends of the slot as appears from Fig. 5. Grooves 26 are formed in the opposite parallel sides ofthe presser block 22 in line with the pins-25, but these grooves Y2li do ,not extend throughout the height of the presser block, with the result that shoulders 21 are provided. These shoulders. 2l will contact the pins25 upon outward movement of the presser block 22 and prevent v,complete removal of the presser block.

When the bushing I8 is located `in -thesccket |5 it should be so oriented that set screw 9 will bear upon the presser block 22 as shownin Fig. 2. The set screw 9 thereforey not only will clamp the Ydrill 2| in place between the `face 23 and the faces 2U, but in addition will serverto clamp the bushing I 8 against displacement from the socket I5.

An important advantage obtained by the Abushing of the invention is that the drill is Iclamped throughout the length of the bushing. This is because the drill lies against Vthe faces 20 `at the bottom of the slot along the entire length of the bushing and because the face 23 of the presser block likewise bears upon the drill 5 along the entire length ofthe presser block.

Drill breakage will be reduced because the end face of the bushing I8, which is toward the drill, and the corresponding end face of the presser block 22 are substantially flush and the clamping up tothese Vvush end faces. Thus, thel clamping action Vis exerted at three places around the drill up to the lendmost point of contact along the drill toward the drill flutes.

A further advantage of the bushing of `the invention vresides in the fact that the drill is contacted at three places about its periphery. .Because of this lthree-point bearing, the drill is securely clamped againstsidewise displacement in any direction. Moreover, due to the threepoint Contact WhichA is afforded, aldrill maybe replaced by another one of the same size and have the4 axis of lthe-new drill occupy the exact position of the former drill. This isbecauserthe -GO face 23 and clampingfaces 20 contact the drill` converging faces 32 at the bottom of the slot is slightly beyond the axis of the bushing 3D. To ypermit the face 33 of the presser block 3| to "bear upon asmalldrill 35 at the bottom of the slot, this face 33 vis only of small width and the converging faces 3d are elongated so that the face 33 lies at a considerable distance from the outer face of the presser block 3|. With the bushing of Figs. 6 and 7 therefor a limited range Vof small size drillsmay be held in place.

It Will be apparent that variations from the proportions shown in Figs. 4 and 6 may be made to provide a bushing and presser block which will accommodate drills of a different range of sizes. Any one bushing and its associated presser block will accommodate a number of different sizes of drills within a vcertain range. The limits of this range are determined by the thickness of the presser block and the depth of the slot in the bushing. Thus, a drill of too small a size will Ynot be contacted by the face of a thin presser block, when the presser block is in its innermost position. Nor will a drill of too large a size be insertable in vplace, if the presser block is too thick as the presser block will project outside of the bushing. l

The range Vof drills which may be held-in place by any onebushing is also limited by the extent, permitted by holes I6, to which the base ange I3 may be moved about the face plate I0. This follows from=the Yfact that the axis of each different size drill which is located in any :one

bushing will occupy a different position from the axis of the bushing itself. To compensate for thisdifferent positioning of the axes of drills of diiferent sizes and to bring the axis of a particular drill into axial alignment with the center o f the work, it is merely necessary to loosen the nuts I'I and move the ange I3 upon the face plate I0 and then tighten the nuts.

What I claim is: f y f 1. A drill bushing comprising a body having .longitudinally thereof a slot-against the bottom .Wall of which a drill is tobeheld, and a presser of 'the presser 4block from the slot.

2. In a tool holder, a generally cylindrical shaped bushing having a longitudinally extending slot therein open; at the periphery of the bushing along the length thereof, vsubstantially parlallel side Walls definingl the circumferential width of saidslot,4 a presser block within` said slot movablemwardly of the bushing forV engaging and clamping a tool in the slot, substantially parallel side walls defining the width of the presser block arranged closely adjacent the side walls of said slot, a side wall of said presser block having a groove therein terminating in a shoulder at an inner end of the groove, and a pin carried by the bushing extending in a generally chordal direction into said groove.

3. In a, tool holder, a bushing having a longitudinal slot therein open at the periphery of the bushing along the length thereof, substantially :parallel side walls dening the circumferential extent of said slot merging with two substantially flat surfaces converging inwardly of the body and meeting on a line beyond the longitudinal axis of the bushing, a presser block tting between said parallel walls of the slot and movable radially inwardly and outwardly of the slot, an innermost flat face on said presser block extending throughout the length thereof adapted to bear against and urge a tool against said converging surfaces, the innermost face of said presser block being of less width than the portion defined by said parallel side walls and being joined to the opposite side walls of the presser block by faces having substantially the same inclination as thel converging surfaces at the bottom of the slot, a bushing holder having a socket therein for receiving said bushing, a radially arranged screw thread through said bushing holder adapted to engage and move the presser block inwardly of the slot and retain the bushing within the bushing holder, a flange carried by the bushing holder having openings therein, supporting studs extending through said openings, and said studs being of smaller dimensions than said openings whereby the bushing holder may be adjusted relative to said studs.

CHARLES F. FINK. 

